Summary

The aim of the project is to find an alternative to hot water immersion. Preliminary research during several years with different oxidative substances and products (H2O2, per-acidic-acid, nitrite) and with Ozone did not reveal sufficient control. Among the variou apple storage diseases, Gloesporium sp. causes extraordinary difficulties with organic fruit compared with conventional fruit. This is due to the fact that organic fungicides sprayed against scab or powdery mildew have no effect on Gloeosporium spores. Thus, infection can cause very severe losses with up to 80-100 % with sensitive cultivars such as Topaz or Pinova. Currently the Gloeosporium disease can be partly controlled by post-harvest by immersion of the apples in 50-52 Degree Celius hot water. Although this method is approved by the organic standards and reliably prevents the spreading of the disease its disadvantages are i) high equipment costs ii) high energy consumption iii) pre-harvest infestation is not controlled and becomes visible after immersion. The project aim is therefore to develop alternative post- and pre-harvest methods to control Gloeosporium storage disease in organic apple growing. Methods applied are - Pre-harvest treatment with organic fungicides on the varieties Pinova and Topaz. - Post-harvest dipping in cold water electrolyte solutions. Hot water dipping is the reference treatment. Results Since 2004 we have had significant control success with the use of clay powder for pre-harvest control and with dipping in cold water electrolyte-solutions for post-harvest treatments. Both control strategies, pre- and post-harvest have to be verified and optimized. Additionally, the technical equipment for fruit dipping in electrolyte solutions has to be developed for practical conditions.